1. Field of the Invention
The present invention relates to the field of multichannel recording systems and more particularly to a novel apparatus for generating accurate calibration signals in alignment with signal data supplied from multiple channel sources in order to eliminate measurable time shifts between recorded and playback data.
2. Brief Description of the Prior Art
In the utilization of multichannel recording systems, problems and difficulties have existed which reside in connection with problems of fine time domain adjustment. There are numerous physical and electrical phenomena that cause the playback of previously recorded signals to be out of phase from the original signal. As the speeds of recording are reduced with respect to the recorded frequencies, this can manifest itself as a measurable time shift. There are numerous physical measurements that can be corrupted by such time shifts.
As an example, in the measurement of physiological signals, the relationship of pacemaker activity to other measured quantities is critical and the reproducing of original signals from the pacemaker must be identical and include no misalignment or time shift variation. Furthermore, in the combining of multiple signal channels into a synthesized signal, time shifts can greatly distort or render the resulting signal meaningless. Any physiological system where measurement locations in one channel are extended to other channels, proper alignment of the signal information between the two channels is critical, such as in ST segment analysis. Additionally, it is often desirable to synchronize the signals whenever the signals are viewed or displayed so as to prevent errors in interpretation.
Therefore, a long standing need has existed to provide an accurate time alignment between signal data derived from multiple recording channels. Prerecorded signals from multiple channels must be synchronized in both amplitude and time so that all channel data is in "phase" alignment, such as vertical alignment of signal pulses between a plurality of inputting channels.